British marine algae : being a popular account of the seaweeds of Great Britain, their collection and preservation

Introduction

Visitors to the seaside frequently complain of the want of amusement and occupation there. I will endeavour to suggest a source which will supply at once amusement, occupation, and instruction. Most people are fond of flowers, and many there are who know something about them ; but how few among them know anything about seaweeds ! The object of this book is to call attention to the beauties of marine vegetation, and to help, by means of accurate and characteristic illustrations, to the recognition and appreciation of the many lovely plants which either in thoughtlessness or ignorance people cast aside or tread under foot as they wander on the sea shore.

The vegetable kingdom is classed under two grand sub-divisions, described by botanists under the terms Phanerogamia, or flowering plants, and Cryjptogo/mia, or flowerless plants. In flowering plants are recognised, in all periods of life beyond the earliest, two distinct kinds of the product of the growth ; these are an axis or stem, and leaves and flowers, the latter being succeeded by the perfect development of special organs containing the fruit or seed of the plant. In seaweeds there is no corresponding arrangement of seed-producing organs, the axis or stem only is represented, but never clothed with leaves and floral organs capable of producing seed vessels. The stem assumes a remarkable variety of forms, in some instances simulating those of perfect leaves, but never presenting that distinct separation into leaf and stem, such as we observe in the chaiacteristic structure of flowering plants. The leaf -like and branching expan¬ sions of seaweeds perform at once the office of stem, root, and leaf, and represent what in the cryptogamic division of plants is termed “ frond.”

Seaweeds, like all other plants which belong to this great sub-class, are reproduced by a simple kind of seed called spore, in which (so scientific botanists say) no embryo or rudimentary plant exists at the period when it is thrown off by the parent plant. Thus the term “ spore ” is now applied to the reproductive bodies of all flowerless plants, while that of “ seed ” specially belongs to the ovules of all the Phanerogamia , or flowering plants. The spores of seaweeds are produced in variously-formed capsules, which in some are borne on the branches, and in others are immersed in

b 2

BRITISH MARINE ALGJE.

membranaceous expansions. Their form, situation, and characteristic dis¬ tinctions, will be fully described in connection with the figures of species which will form the illustrations to these pages.

There is one fact which makes the study of cryptogamic botany peculiarly interesting, and that is that a large portion of fossil vegetation is very intimately related to some of the nobler flowerless plants, and probably exhibits far grander and more highly organised individuals than any which at the present time are found in a living state. The celebrated Hugh Miller informs us that fossilized algae were not discovered until so recent a period as the year 1856, when some of the fucoids, or kelp-weeds, were detected in some ancient rocks in Shropshire. In the ancient Lower Silurians of Dumfriesshire, these rock weeds were so abundant that they have produced large tracts of anthracite coal several feet in thickness. The string-like plant known as Chorda filum, or popularly, “ dead mens’ lines,” had a Lower Silurian representative, known to the palaeontologist as Paloeochorda, or ancient rope. The well-known “ Carrageen moss ” of the Irish had also a Lower Silurian prototype, and our Fuci or rock kelpweeds were represented by Fucoides gracilis of the Lower Silurians of the Malverns ; in fact, the Thallogens of the earliest periods of vegetation appear to have resembled in their general characteristics the algae or sea¬ weeds of the present era.

Were I to attempt to give a history of the various systematic arrange¬ ments by different authors, or of the steps by which we have arrived at our present knowledge of marine vegetation, I should certainly weary the reader ; therefore I will state at once, that the plan I shall adopt in these pages is based on the system of the late Professor Harvey, of Dublin, as recently revised by Professor Agardh, the celebrated Swedish algologist. These admirable botanists have distributed the algaa into three large groups, which may be briefly described as follows : First, or simplest in point of structure, Chlorospermece , mostly grass-green, but varying occa¬ sionally to olive, purple, or other tints ; Melanospermece, olive-green, sometimes inclining to yellow or brown-olive ; and Bhodospermece, rose-red, with every variety of pink, red, or brown-red tints, sometimes purple, but very rarely green. These three great sub-divisions are separated into orders, genera, and species. The Chlorosperms consist at present of six orders and twenty-three genera. The Melanosperms of six orders and thirty-five genera, and the Khodosperms of thirteen orders and sixty-six genera. The name alga, which, as Dr. Harvey says, formerly included the lichens, is now limited to that large group of flowerless plants which con¬ stitute the characteristic vegetation of the waters, the marine division of which is now popularly termed seaweeds.

Seaweeds may fc>e characterised as cellular flowerless plants, living in or entirely under water, and deriving nourishment throughout their whole substance from the medium in which they vegetate. Roots, properly so called, they have none ; the base of the plant, by which it is attached to the rocks or other substances, serving merely as a holdfast, to prevent the

I

INTRODUCTION.

plant from being driven about and destroyed by the action of the waves ; but as no vessels of absorption have hitherto been discovered in the roots and stems, it is .evident that seaweeds do not derive their nourishment from the substance to which they are attached, for indeed they are found growing luxuriantly alike on iron and floating timber, on rocks and shells, on the carapaces of crabs, and even upon each other, in the latter case without any detriment whatever to the species on which they are parasitic. The roots or holdfasts in some are a flattened or slightly conical disc, in others branching and clinging fibres, and in the Laminarias or oarweeds, especially as the plants advance in growth, a series of grasping processes are thrown down from the stem, which adhere so firmly to the rock that it is extremely difficult to detach them.

The algge, or seaweeds, consist entirely of cellular tissue — little mem¬ branous sacs or cells of various forms, with walls of different degrees of tenacity. These minute cells are empty or filled with granular organised matter, which divides and developes new cells ; these again divide and produce others, and thus by this eell splitting, branches and spreading fronds or leafy expansions are produced, each order of

cell-division proceeding according to the laws of growth of its own species. The cellular tissue of which all seaweeds are composed presents several varieties.

The most common form of cell is that of a cylinder, generally much longer in propor¬ tion to its breadth, and when such is the case the cells are attached end to end, forming threads or filaments, numbers of which, branched or otherwise, make up the frond by becoming firmly attached in bundles. Many of the simpler kinds of seaweeds are made up of threads or strings of cells, some of which are elaborately branched, others unbranched, yet through-

Fig. 1. Filament of Conferva tortuosa. out the whole plant the cells or joints are Fig. 2. Cladophora Hutchinsice. • • ■> i j . , ■ , . . ,

Fig. 3. Sporeclothed with cilia (white variably produced in the unbranched

or coloured). kinds from the tips of the cells of those

niata. beneath them, or from the upper side, as

well as from the tips of the joints in the

branching species. A portion of a filament of Conferva tortuosa (Fig. 1)

and a branchlet of Cladophora Hutchinsice (Fig. 2) will illustrate the

simple cellular or jointed structure of branched and unbranched filaments.

Polygonal and other forms of cells are found in the leafy and membranous

species, the particular forms being in most cases due to cell-pressure

during growth, some adhering very closely together, and accommodating

their forms to the spaces they have to fill, while in others the cells are set,

as it were, within a transparent gelatine, each cell being completely sepa-

BRITISH MARINE ALGHC.

rated from its neighbour by a hyaline or colourless space or border. The contents of the cells which give to the plants their various hues are termed endochrome or chlorophyll, and it is from this colouring matter in con¬ nection with a partial metamorphosis of certain portions of some species that the fructification of seaweeds is produced. Of the various forms of fructification and other particulars connected with the different systems of reproduction I shall speak as occasion arises. Thus much, however, I may state at once, that in speaking of the reproductive bodies of some of the green plants, the term “ zoospore,” in addition to that of spore, will be occasionally used, the word zoospore signifying animal seed, from the peculiar movements it exhibits in the water by means of the filaments with which it is furnished.

When examined by the microscope, the spores of most of the seaweeds at the time of their emission from the cells of the parent plant are found to be clothed with very minute hairs, the constant vibratile motion of which causes them to move about with the greatest activity. “ The little spore,” says Professor Harvey, “ whilst contained within the mother cell, commences life by knocking continually against the walls of the inclosure until it has burst through them into the surrounding water, and then with many gyrations and rapid changes of place it swims about by means of the cilia with which it is clothed, until it finds a substance on which it can rest and attach itself. Once fixed, or apparently satisfied with its locality, its youthful wanderings are over, and its seemingly voluntary motions cease. The cilia are absorbed or perish, and the vegetable cellule com¬ mences the growth natural to its kind, and finally becomes a plant resembling the species from which it sprang.” A spore is represented, of course very highly magnified, by the little oval figure (Fig. 3) in the group of diagrams.

Among the various uses of seaweeds in the economy of nature, especially among the green plants, is that of the power they possess, although in a small degree, of contributing to the purification of the water in which they live. This is due to the oxygen which is generated in their delicate tissues, from the carbonic acid which they absorb from the surrounding water. Few marine animals will live long healthily in the confinement of aquaria, unless the water be properly supplied with growing plants of Ulva and other green seaweeds.

In an interesting little work on British Seaweeds, by the late Dr. Lansborough, I remember reading an account of a rebuff given to an enthusiastic young student by a professor of botany, to whom he had shown the contents of his vasculum, after a day’s gathering on the sea shore. “ Pooh, pooh, sir,” said the old gentleman, “ a parcel of seaweeds — pah.” Nice encourage¬ ment this must have been for a botanic student, perhaps an incipient algologist ! This reminds one of the “ Alga projecta vilior” of the old Eoman poet — terms of contempt for the beauties of the deep, which, I suppose, must be forgiven, in consideration for the glorious verses which the speaker has bequeathed to us. However, as regards the old professor

INTRODUCTION.

of botany, it is very probable that the extent of bis acquaintance with sea¬ weeds was limited to the rejectamenta of the sea ; for the rebuff referred to took place some sixty or seventy years ago, at which period a knowledge of seaweeds was very scanty indeed ; numbers of species which are now familiar to every collector had not then been discovered, the dredge was hardly in use, and the microscope was in its infancy. Things, however, are very different now, and there is really no excuse for people who may desire some acquaintance with marine algae, talking of the difficulty of finding beautiful plants, of learning their names, and of mounting and arranging them. I have very often been appealed to for information as to the best method of acquiring knowledge on this subject, and my invariable advice has been, as I write it once more, read some standard work on sea¬ weeds in the first place, study the figures of the plants, for indeed good illustrations are indispensable to a perfect comprehension of the best des¬ criptions of species, and then go and gather the flowers or weeds of the ocean, call them what you will, and he or she must be a churl indeed who is not quickly fascinated with such an occupation, which not only brings health unsought, but elevates the mind, and thus by pointing through nature up to Nature’s God, enlarges man’s ideas of the wisdom, power, and goodness of the Creator.

I have often been amused to see the strange, not to say absurd, mistakes made by beginners in naming their plants ; and I doubt not many a botanist as well as myself has been provoked at the disinclination so frequently evinced by amateur collectors to anything approaching study by means of the microscope, as though it were possible to acquire know¬ ledge in botanical pursuits without its help, or at least that of a good lens or magnifier. Look, for instance, at the Cladojphora , to a few of which I shall call the reader’s attention by means of my figures of magnified branchlets. True, an experienced algologist knows at once what is the species he has before him, but he did not always know it, and, although the eye soon learns to detect differences in appearance, knowledge of specific distinctions among the filamentous aud delicately-branched seaweeds can only be acquired by means of the microscope.

SECTION I. CHLOROSPERMEiE

Green Seaweeds.

Among the most abundant of the common species of seaweeds are two, TJlva latissima and Porph/yra laciniata , which form together, when pre¬ pared and potted, the laver of commerce ; the latter, although belonging to the chlorosperms, in accordance with its system of fructification, is brown, or sometimes a lurid purple. There are several tolerably welldefined species of each of these plants, some of which are found abundantly on rocky shores, while others are somewhat rare. The species most com¬ monly met with is Ulva latissima (Fig. 5), or the very broad TJlva, or

Fig. 5. Ulva latissima.

familiarly, lettuce weed or green laver. This species is found on all shores and in all latitudes, except in the Arctic regions, though even there a small stunted species called TJlva cvispa is sometimes met with. The frond of Ulva latissima is delicately membranaceous and of a bright green colour ; in form it is usually a broad, rounded oblong, from 6in'. to 14in. long, often very much waved at the margin, and attached to the rocks by a very minute disc. The spores are usually arranged in groups of fours, and are scattered over the whole frond.

CHLOROSPERHEiE.

Ulva linza (Fig. 6), a beautiful and very graceful species, though by no means rare, is not so abundant as the former plant. It grows in similar situations, and sometime^ even in society with it. The plant consists of a cluster of fronds from 6in. to 2ft. in length, about l|in. in width, and tapering gradually to the base. The f roads are generally very much curled and waved at the margin, and the whole plant is of a bright grass-green colour. The frond of this species consists of two delicate membranes, the cells of which are divided vertically and horizontally, so that they are at once leaf -like and tubular. To ordinary observers, this plant bears a strong resemblance to Enteromorpha intestinalis ; and, indeed, Dr. Greville, of Edinburgh, in describing this species, points out the fact of its double membrane, forming at least a transition to the genus Entero¬ morpha. Collectors, however, after a very little practice in comparing specimens of these plants, will not have much difficulty in distinguishing them ; Enteromorpha intestinalis being always tubular and somewhat con¬ stricted at intervals, while Ulva linza is comparatively flattened, never constricted, and always more or less waved at the margin. Porjphyra lacinmta bears a striking resemblance to Ulva latissima, not only in out¬ ward form, but in its fructification, which consists of sori or groups of spores. Under the microscope the whole membrane of the plant appears to be divided into segments or square groups of cells, regularly arranged in fours, and within these squares are contained four purple spores, as seen in the illustration (Fig. 4). Porphyra, under the name of laver, is boiled and eaten with lemon juice or vinegar, and is not only very wholesome, but agreeable in flavour, and were it not for the ignorance and prejudice which sailors exhibit concerning things they know not, this common seaweed might become a valuable article of vegetable diet to the crews of whaling vessels and voyagers in the Artie regions, since nearly every marine rock is clothed with its dark brown, fronds. The plant in our illustration (Fig. 7) is Porphyra vulgaris, a much more elegant species, being narrower, much longer, and very gracefully waved and curled at the margin, some¬ what like Ulva linza. The colour of Porphyra is a very singular departure from the ordinary green tint of the Chlorosperms ; the plants of this genus being, in the living state, of a dark brown, which after drying and mounting on paper changes gradually to a fine purple, or sometimes to a rose red.

The order Ulvticece contains a genus of interesting plants which at present must be merely glanced at, for in the first place they are, with the exception of one species, nearly microscopic, and, secondly, anything like a description of them will necessitate illustrations, most of which would be too minute for the purpose I have in hand, viz., popular information. I will merely state, then, that the genus to which I refer is named Bangia, in honour of Hoffman Bang, a Danish botanist. All the species of Bangia are purple, or sometimes inclined to brown-red, and they are mostly parasitic on other algae ; one species, and that the largest, being found near high-water mark, growing on rocks and wood. Its name is Bangia fusca-purpurea. Inexperienced collectors would hardly imagine this plant

BRITISH MARINE ALGiE.

to be included in the Chlorosperms or green seaweeds ; and this is another instance of the necessity, as already pointed out by me, of some little book-learning at first, otherwise many a pretty plant will be passed by unheeded or overlooked. The species in question consists of a bundle of purple silky filaments, several inches long, unbranched and very narrow throughout their whole length. The broadest filaments of this delicate plant, under the microscope, are seen to be tubular, and to contain four or five rows of granular cells, a form of structure which connects these plants with the Ulvacece, otherwise to the ordinary observer, they would appear to belong to the Confervce, a genus of green unbranched plants which I will describe presently.

The Enteromorphce, of which two common species make their appearance about high-water mark clothing rocks and stones with a slippery vesture of shining green, have been the cause of many a tumble to the unwary pedestrian on the sea shore. I have heard these pretty green plants some¬ times called “ sea-grass” and “ mermaids’ hair,” and, indeed, some of the rarer and finer species may well be termed mermaids’ hair or sea hair. But first I must describe the two species that are met with everywhere, and these are Enteromorpha intestinalis and E. compressa. The former grows in tufts, and is simple, or unbranched ; each frond is tubular, and somewhat constricted here and there, and in form resembles the intestine of an animal, hence its specific name ; but E. compressa (Fig. 8) is a branched species, and is compressed or flattened at the margin. These plants are very variable in length and width, the filaments of some specimens being very narrow, while others are as broad as Ulva linza, and very dark in colour. The largest specimens of Enteromorpha always appear to me to owe their unusual size to the action of fresh water ; I have often seen specimens of E. intestinalis, as well as Viva latissima, growing in streams which were scarcely even brackish, more than 2ft. in length, and of such breadth that they appeared like large green bags floating in the water. The structure of the Enteromorphce is very similar to that of Ulva ; the whole frond is beautifully reticulated, the cells being arranged in fours, or multiples of that number, the endochrome or colouring matter of which at maturity is converted into spores. The fronds of these green plants are often found partially white, and sometimes wholly so. This is due not only to incipient decay, but because the spores have broken away from the cells, leaving the membrane of the plant colourless and unsightly. Then is the time to look for certain rare microscopic parasites, some of which have their special habitat on decaying fronds of Entero¬ morpha, as well as on those of the Ulvoe. In addition to these two well-marked and easily recognised species, there are several others, more or less rare. Among these, the most interesting probably is the species called E. clathrata (Fig. 9). It grows abundantly in the rock pools all about Torbay, but being a summer annual, it loses much of its bright green colour towards the end of September, and soon after turns to a brownish yellow* In all stages of its growth the fronds are extremely slender, very much

Conferva Youngana.

Fig. 9. Enteromorpha clathrata. Fig. 10. Cells with binate sporangium.

Fig. 11. Portions of iilaments.

CHLOROSPERMEjE. 13

branched, and set throughout with short, spreading, or recurved ramuli or branchlets.

There are several species of Enteromorpha, which, to ordinary observers, so strongly resemble each other that reference to the microscope is absolutely necessary to distinguish them. At the head of these stands Enteromorpha clathrata, just mentioned ; the others are now classed as varieties of this species, but, although I intend to figure only one of them, chiefly on account of the grace and beauty of the specimen I possess (which is also highly characteristic of the species), I will endeavour to point out certain peculiarities of growth in each of them, so that they will be more readily recognised by inexperienced collectors. I therefore direct the reader’s attention to the figure of E. Linkiana (Fig. 9a). The frond is about 6in. or 8in. in height, with a distinct main stem, throwing out along its whole length branches several inches long, smaller in diameter than the main stem, and bearing in their turn a second and third series of very fine hair-like branches or filaments, all of which spread out, but incline upwards. E. erecta has also a distinct main stem, but the branches, which are set on each side of the stem, are more regular in length and are clothed with finely attenuated ramuli, which taper to a needle-like point. In E. ramulosa, the main stem is less definite than that of the two former speeies, the fronds are tufted and the branches, which are numerous, but of irregular length, are bent, or somewhat curved, in various directions ; the ramuli are short and bristle-like, and are set without order on the branches from the base to the tip. The fronds of all these species are all more or less reticulated like a tessellated pavement, and within the cells of the surface the spores are formed, generally in groups of fours. E. cornucopia is a singular species (if, indeed, it really be a species), usually found on Corallina officinalis and other algae. In early growth the fronds are like little elongated bags, which soon break at the apices and expand into the form which has suggested their fanciful specific name ; some botanists regard this plant as merely a form of TFlva lactuca , which, in the young state of that species, it certainly very strongly resembles. Other smaller and rarer species of Enteromorpha are known under the names of distinguished botanists, and these are E. Ralfsii and E. Hopkirkii. There is also one other variety of E. clathrata known as E. percursa.

E. Linkiana, E. ramulosa , E. erecta , and E. percursa were formerly regarded as distinct species, but are now considered as variations of E. clathrata. The differences in character are hardly appreciable to any but practised botanists, hence a particular description of all of them is scarcely necessary, at least in a popular account of British seaweeds.

The genus Conferva formerly included a large number of green plants branched and unbranched, but it is now confined exclusively to a definite number of filamentous algae, which are made up of masses, more or less tufted or matted together, of strings of cells or joints, which increase in length, either by a species of budding from the terminal cells of the fila¬ ments, or from a continual division of the old cells in the centre. The latter

BRITISH MARINE ALGvE.

mode of growth is most general among the Confervce proper, which are all unbranched. Recourse to the microscope is necessary for an examination of their structure, and also to identify species. These simple plants are propagated by zoospores, which are formed from the granular con¬ tents of the cells, or from the whole mass of endochrome or colouring matter of one or more cells being concentrated into an enlarged cell and forming there a sporangium or spore - bearing conceptacle, from which, on the perishing of the old plant, new individuals are propa¬ gated. Fig. 10 represents a por¬ tion of a filament, highly magnified, of Conferva Youngana, the central joint of which contains a binate sporangium. Fig. 11 represents portions of two filaments of the same species, highly magnified.

Most of the Confervce inhabit fresh water, and are found abun¬ dantly wherever stagnant water

-ft

Fig. 12. Conferva tortuosa.

lies, the oxygen which they continually throw off into the air, helping to neutralize the noxious effects which would otherwise arise from decaying vegetation in the water beneath them. The marine species of Conferva are not now very numerous ; one of the most common perhaps is Conferva tortuosa, well represented in the illustration (Fig. 12), a magnified filament of which was engraved on p. 5 (Fig. 1). This species is mostly parasitic on old stems of the Fuci, near high water mark ; but the masses of its entangled tortuous filaments are so inextricably interwoven, that it is useless attempting to separate them. The name Conferva is from the Latin Conferruminare, to consolidate, the ancients having made use of masses of these plants in binding up wounds and fractured limbs.

Among the Confervce there are two species By no means uncommon, which at a cursory glance strongly resemble each other, especially when they are seen growing in the water. One of them, Conferva cerea, is found on sand-covered rocks about half-tide level, growing in a tuft of erect filaments from 3in. to 4in. in length. The articulations or joints of the filaments are about as long as broad, and the whole plant, though harsh to the touch, loses its rigidity, and lies prostrate as the tide recedes from it. A plant of Conferva cerea is shown in (a) Fig. 12a, and beside it a fragment of a filament magnified to show the form of the cells. The other species ( b ) is Conferva melagonium. It is usually found in rocky tide pools, where its long bristle-like filaments, from 4in. to 12in. in height, stand erect, stiff, and straight, even when left uncovered by the ebb of the

CHL0R0SPER.ME2E.

Fig. 12a. (a) Conferva area, and portion of filament magnified ; (b) Conferva melagonium, and three cells magnified.

tide. All the articulations, except the lowest, are about twice as long as broad, the endochrome or cell contents being of a dark green colour. A plant of this species is represented at b, and beside it, three joints from the

centre of a filament.

The long filaments of this species are gene¬ rally few in number, and are set some little dis¬ tance apart, while those of C. cerea are more numerous, and grow in tufts closely packed to¬ gether. I have described these two plants under the names by which they have been long known, but I must inform my readers that their generic name now is Chcetomorpha, which is at once significant and charac¬ teristic, as having refer¬ ence to their bristle or hair-like appearance. Of course a good lens is indispensable in examining these minutely -jointed plants, otherwise specific distinctions cannot possibly be understood and appreciated. For ordinary purposes a watch¬ maker’s eye-glass is sufficient, but to those who will take the trouble to acquire its use, a Stanhope lens is the algologist’s true vade mecum.

I now come to the puzzling but beautiful sub-genus, Cladophora, or branch-bearers. All the plants belonging to this family are branched, some most elaborately so ; several species are very rigid and exceedingly difficult to display on paper, becoming often so entangled and interwoven as to tire the patience of the most expert manipulator. They are pro¬ pagated by a conversion of the granular contents of the joints or cells into zoospores, which, upon being cast loose from the cells of the plant, swim about like so many tiny animalcules. The process of development in the zoospores or reproductive bodies of the Cladophora is so exceed¬ ingly interesting, that I direct the reader’s attention to the group of figures (13, 14, 15), which represent the different stages of development in the endochrome or cell contents of Cladophora Icetevirens. Fig. 13 represents a highly magnified portion of a filament at the moment that the terminal joint has formed a kind of wall or line of division, this being the first step in the process of cell division, and which results in the separation of the endochrome into two portions. Beside it (Fig. 14) is a filament with the cells and zoospores fully developed. On the upper and right wall of each cell is a slight projection, or expansion of the cell